Asbestos filled drier felt



Nov. i6, 1937. w. A. BARRELL 2,098,993

ASBESTOS FILLED DRIER FELT l Filed Aug. 15,' 1935 g Mgmt j @l PatentedNov. `I6, 1937 UNITED STATES ASBESTOS FILLED DRIER FELT William A.Barrell, North Andover, Mass., assignor to Lawrence Duck Company,Lawrence,

Mass., a corporation of Massachusetts Application August 15, 1935,Serial No. 36,291

8 Claims.

This invention relates to' drier felts for paper machines andparticularly those which contain asbestos in their construction as aprotection against the effects of heat and moisture to which such feltsare subjected and to use beneficially the moisture absorbing propertiesof asbestos.

Objects of the invention are to produce a drier felt combining theadvantages of a substantial content of asbestos with greater tensilestrength and lighter weight than the asbestos feltsin use prior to thisinvention and related inventions for which I have sought and securedpatent protection; and to combine the strength due to a warp madeentirely of cotton (or other fibers substantially equivalent to cottonin regard to strength and relatively light weight in comparison withasbestos) with minimum liability to stretch in length and contract inwidth under the severe tension to which drier felts are subjected inuse. Another object is to prevent seepage of oil and grease from thedrums of the drier into the asbestos content of the felt, suiiicientlyto avoid contact of oil soaked strands and bers with the paper as longas the felt remains otherwise serviceable. K

In carrying the invention into effect I construct my improved felt withcotton warp and asbestos filling, Woven in two plies with binder Warpstrands passing between the two plies at points numerous enough toeffect a secure connection between them. Instead of cotton for the warpI may alternatively use other fibrous material having adequate strengthand which is also light enough in weight to meet ,commercialrequirements, such other fibers being considered as equivalent to cottonfor present purposes. The

important point is that asbestos strands are not used for any part ofthe warp, but the entire content of asbestos in the felt is contained inthe filling, and is so disposed as to absorb moisture readily andquickly from the paper, and to protect the cotton against thedestructive effects of heat and moisture so eiectively as to assurelong,

` efficient and economical life of the felt.

An illustrative embodiment of the invention is described in detail inthe following-specification and shown in the drawing, in which,-

Fig. 1 is a plan view of the face of such illustrative embodiment;

Fig. 2 is a plan view of the back of the same;

Fig. 3 is a section on line 3-'3 of Fig. 1, taken in the direction ofthe lli'ng;

Fig. 4 is a section taken on line 4-4 of Fig. 1 in the direction of thewarp of the felt;

N. Bf. The foregoing gures are`drawn in approximately correct ratio tothe actual felt, but on a larger scale for clearness.

Fig. 5 is a section on line 5 5 of Fig. 1, showing the disposition ofthe binder strands;

Fig. 6 is a fragmentary section of one of the selvage edges of the feltto illustrate one form of means to stop oil seepage from the drums ofthe drier into the body of the felt;

Fig. 'I is a fragmentary plan View of a. portion of the felt, on a muchreduced scale, to show the oil stops at opposite edges;

Figs. 8 and 9 are detail views, on an enlarged scale, of alternativetypes of asbestos filling yarn which may be used in the construction ofthis felt.

Like reference characters designate the same parts wherever they occurin all the figures.

This felt is composed of two plies of woven construction, designated Aand B respectively. Each ply is Woven of cotton warp and asbestos lling,as a plain Weave; the warp strands of the ply A being designated a, aand the filling a2, while the warp strands of the ply B are designatedb, b', and the filling as b2. The two plies are connected together bybinder Warp strands c which pass over and under filling strands a2 andb2l alternately.

An important feature of the invention is that the asbestos filling yarnis made soft and bulky, considerably larger in diameter and softer intexture than the warp strands, whereby the latter sink deeply into thefilling strands and are themselves much less bent than is the case with-warp strands interwoven with hard lling. It follows from this that theasbestos lies in both surfaces of each ply, but the asbestos strands arenot much crimped, (i. e. bent or offset, and shortened) The substantialabsence of crimp `in the weft strands and the comparative straightnessof the warp strands lessens the tendency of theA felt to contract inwidth under the tension ap plied to it in use. However, it may be -notedthat such further straightening of' the warp strands as occurs under thesevere tension applied to the felt in the drier causes the warp strandsto sink still further into the asbestos strands and makes the asbestosmore prominent in the surface.

The asbestos in the face of the felt which comes next to the paper isdistributed regularly over this entire face and, owing to the originallylarge size of the asbestos filling yarn and its ability to spread underpressure, forms a major part of this lface. It absorbs moisture at allof the numerous and closely adjacent areas where asbestos comes intocontact with paper. Thoseportions of the asbestos filling which lie inthe inner surfaces of the two plies (which for convenience ofdescription may be referred to as asbestos tuftsl make contact with eachother at many points, some of which are denoted in Fig. 3 by thereference letters d ande, whereby the asbestos in the back ply forms ineffect a continuation of the capillary moisture-conducting paths ofasbestos in the face ply. Where these portions or tufts of asbestos cometogether, the equivalent of continuous Wicks are created leading fromthe face to the back of the felt. Thus moisture absorbed from the paperis. conducted directly through the felt to the back and evaporated at amultiplicity of points into the outer air.

Preferably, although this is not an essential, the weave of the faceply, here represented as the ply A and being the ply which comes next tothe paper, is made of more open weave than the back ply B, by havingfewer warp strands. This has the effect of relatively increasing theproportion of asbestos exposed on the outer or front face of the felt.The specific felt here illustrated is a plain weave made with twelveends of warp per inch of width in the face ply, controlled-by twoharnesses in each of which are six ends of warp, twenty-four ends ofwarp per inch of width, in the back ply, also controlled by twoharnesses, and six ends of binder warp per inch, controlled by a fifthharness. There are twentyseven picks of filling per inch. The asbestosfilling yarn has substantially twice the diameter of `the warp yarns,which latter are of the same diameter in both plies. The binder yarnsare much finer than the body warp yarns and are substantially coveredand protected by the latter in both outer faces of the felt. Even thoughthe ends of ywarp in the back ply are fewer than in commercial allcotton drier felts of two ply construction heretofore made with warpstrands of the same size, yet the felt as a whole is not subject to asgreat stretching in length and contraction in width as are such allcotton felts, because of the peculiar interrelationship between the hardwarp strands and soft bulky filling yarn.

It will be understood that the details just given of 'a specificembodiment of the invention are not to be construed as limiting thebroader aspects of the invention thereto. While I claim theseparticulars as a subordinate feature of the invention, nevertheless Iintend to protect under my broader claims substantially equivalent feltscontainingdifferent numbers and weights of strands and in which thenumber-of warp strands is the same in both plies, or in other ratiosthan one to two, and in which the pattern is other than a plain weave.

I:.ihis felt also embodies means to prevent or resist seepage of oilfrom the drums and gears of the drier inward from the edges of the feltfar enough to interfere with drying of the paper.

The heated drums or cans of paper driers are usually more or less oilyor greasy at the ends from the lubricants applied to their journalbearings and driving gears. Asbestos fiber is highly With such felts theoil creeping over the ends of lthe cans is absorbed by the outer edgesof such felts, and gradually accumulates and seeps inward toward themiddle. Eventually the combined effects of seepage and narrowing of thefelt bring oily parts into contact with the edges of the paper. dry sorapidly as the rest of the web, from which moisture is absorbed by theoil-free asbestos fibers and strands of the felt. The only meansheretofore known to obtain adequatey drying' of the edges of the paperunder these conditions are either to reduce the width of the paper webor increase the steam pressure and temperature in the drums. Both ofthese methods are expensive and objectionable; the first because itinvolves diminished production of paper, and the second because itinvolves increased fuel consumption and makes all of the paper exceptits edges too dry. The paper does not calender well, due to insufficientmoisture content, and suffersv a loss of weight.

On account of these diiculties users of asbestos felts have heretoforediscarded them as soon as the factors of oil seepage and widthcontraction have together brought oily parts of the felt into contactwith the paper. But otherwise the felts so discarded have beenunimpaired in usefulness and capable of much longer useful life.

In effecting thel object of preventing or resisting oil seepage, I haveso constructed the margins of my felt that only cotton, and notasbestos, comes into contact with the drums at the margins. The specificmeans here shown for doing this consists in providing so great a numberof warp strandsin the margins of the felt, ,or' atleast in the face plythereof, as substantially to cover the lasbestos filling. Although thewarp strands are relatively hard and firm in comparison with theasbestos iilling yarn, this does not mean that they are incompressible.On the contrary they have considerable capacity for compression anddistortion in cross sectional form. Those at the margins are so numerousand closely crowded together that they compress one another at thecrossing points of the shed, but where they cross the picks of fillingthey spread laterally and lie so near together that they do not sinkinto the filling like the more Widely spaced warp yarns in the mainApart of the felt, and do not leave room for the asbestos to come to thesurface. Sixteen ends per inch of warp in each harness at the margins ofthe felt, when of the same weight as the ends used in the balance of thewarp, are effective for this purpose; and it is feasible thus to weaveeven more ends per inch of the same size yarn, or

a still greater number of thinner strands.

Cotton is inherently much less absorbent of oil than asbestos fiber,while the closer and harder twist under which the cotton fibers are heldin the warp vstrands increases their oil repellent quality.

Referring to '7, which shows a fragment Those parts of the papertherefore do not it does in close embrace with the cotton-strands,

it tends to keep the cotton ina more even con-` dition as to heat andmoisture. In connection with the body warp strands it covers the binderstrands substantially completely in the face of the felt, and sopreserves the strength of thev latter and the close bond between the twoplies even after the cotton in the face of the felt has lost itsstrength and integrity. Thus the felt remains serviceable until long usehas destroyed the strength of the back ply warp.

The characteristics and advantages herein described depend on the use ofasbestos filling which is soft and highly compressible. It is notfeasible to spin asbestos fibers alone so as to Vcombine such softnesswith suiiicient tensile strength to hold together when weaving. Otherstrands or fibers must be used for tensile strength when looseness ofthe asbestos fiber is desired. I have shown here two of the possibletypes of reinforced asbestos yarn which may be used in this felt.

That-shown on an enlarged scale in Fig. ,8 consists of a core h ofstrong twisted cotton yarn, around which is loosely twisted a softenveloping mass y of asbestos fibers. Yarns of this character arealready known. Another form, shown in Fig. 9, is an original inventionof my own. It

consists of an elongated body Ic of lasbestosv cient and ample for thepurpose, although there may be more or fewer. These threads extend witha longhelical lead, the length of which is many times the diameter ofthe yar-n, whereby they form a cage of which the open meshes are solarge that practically unimpeded opportunity remains for the asbestos toabsorb and transmit moisture after being woven. But the confiningthreads prevent particles and bunches of asbestos fiber breaking loosefrom the yarn. Even though after weaving, some parts of these threadsmay overlie the asbestos in the face of the felt,`and be quicklydestroyed in use, their destruction does not weaken the felt appreciablybecause the asbestos fibers are long enough, and confined at points sonear together by the over passing warp strands, that they have notendency to disintegrate.

Such. asbestos filling yarns may be made in different diameters, up tosizes amply large for the purposes set forth. Or two or more of them maybe placed in each pick of the filling.

The mention herein of cotton as the ber of vwhich the nciiasbestosstrands of the felt are made is not to be taken as a.v necessarylimitation of all phases of the invention. Actually cotton is the bestmaterial available and is used commercially to the practical exclusionof other fibers. Blt I reserve the right to use, and to protect under atleast the broader of the appended claims, other fibers of vegetable oranimal origin now known, or which may hereafter be found, to be suitablefor the purpose in combination,l substantially as described, withasbestos liber.

That portion of the invention which resides in the' oil stops may,within the scope of protection claimed for it, be combined with asbestosfelts, or those containing asbestos, of other constructions than thatshown here.

'I'he designation in the following claims of certain strands as beingasbestos strands is intended to include also those in Which other bersare4 associated with asbestos for the purposes previously indicated.

What I claim and desire to secure by Letters Patent is:-

1. A drier felt comprising two plies of inter- -woven nonasbestos warpand asbestos lling, and

binder warp strands crossing picks of the filling alternately in bothplies, the asbestos of the filling being exposed between adjacent warpstrands on both faces of both plies and parts of the filling strands inboth plies being in contact forming substantially continuous absorbentwicks through both plies. l

2. A drier felt for paper machines comprising two plies of interwovennonmineral brous warp and asbestos filling, and binder warp strandspassing around picks of the filling alternately in both plies, the endsof warp in the face ply being fewer and more widely spaced apart thanthe warp yarns of the back ply, and the filling yarn being relativelysoft and compressible by the warp yarns, whereby asbestos is caused toappear on the paper-contact face of the felt in areas which collectivelyform a major part of the area of such face, and at the opposite side ofthe face ply is brought into contact with portions of the asbestosfilling of the back ply.

3. A drier felt for paper machines comprising two plies both woven ofcottonA warp and asbestos lling combined with binder warp strandspassing around picks of the filling alternately in the two plies, thewarp strands of the face ply being spaced sov widely apart, and thelling yarn being so soft and compressible by the Warp yarns as to causeasbestos to appear on the face of said ply in areas which collectivelyforml a major part of the total area of said face, and the back plyhav.- ing twice as many warp strands as the face ply of which alternatestrands are in the same longitudinal planes with the face( ply Warpstrands, and having an equal number of filling strands in the sametransverse planes with lling strands of the face ply.

4. A drier felt for paper machines comprising two plies both woven ofcotton warp and asbestos filling combined with binder warp strandspassing around picks of the filling alternately in the two plies, thewarp strands of the face ply being spaced so widely apart, and thefilling yarn being so soft and compressible by the warp yarns as tocause asbestos to appear on the face of said ply in areas whichcollectively form a major part of the total area of said face, and theback ply consisting of a loose elongated body of asbestos fiber and aconning group of ne threads intervbraided with one another around suchasbestos body with a suiciently wide spacing between them to expose asubstantial part of the asbestos body.

6. A drier felt for paper machines comprising a cotton warp and anasbestos filling interwoven therewith, the lling yarn comprising a soitand loosely twisted body of asbestos fibers and a cage of fine cottonyarns braided around the asbestos with large vopen meshes, the warpstrands being smaller and harder than said asbestos yarn and beingspaced apart suciently to indent the lling yarn and cause portionsthereof to appear on the surface of the felt between the surfaceportions of the warp yarns.

7. A drier felt for paper machines comprising two plies of substantiallythe construction set forth in claim 6,.and binder warp strandsconnecting said plies together, portions of the asbestos iilling at' theinner faces of the two plies being in contact with one another andcollectively vforming wick paths for moisture from the paper.

' substantially fill the-spaces between adjacent warp yarns in the faceof the felt, making a fiat surface.

WILLIAM A. BARRELL.

